Microstructural Changes with N Content in Sm-Fe-N Alloys

The microstructures of Sm2Fe17Nx (0≪x≪6) powders were observed by transmission electron microscopy (TEM). Sm2Fe17N23 powders nitrided in N2 gas have high dislocation densities due to lattice expansion. Sm2Fe17Nx powders nitrided in a mixture of NH3 and H2 gases (3≪x≪6) have cell-like structures. The dislocation density increases and the cell diameter decreases with increasing N content, and Sm2Fe17N5.9 powders consist of 30 to 50 nm in diameter Sm2Fe17Nx microcrystalline grains surrounded by an amorphous phase. Sm2Fe17 powders nitrided above 600°C dissociate into SmN and ¿-Fe phases with characteristic sizes of 10 to 20 nm.